Apparatus for producing case metallic product by forming a metal

ABSTRACT

Process and apparatus for producing a cast metallic product by forming a metal from a melt inside a forming space of a die under application of pressure to the melt according to a direct melt-forming method, in which while a melt into a forming space of a lower die unit, a piston valve closely slidable in a cylinder space is gradually descended to a given location in the forming space, said cylinder space being located under the casing space and opened to a bottom surface of the forming space at an area smaller than that of said bottom surface; the forming space is closed with an upper die unit after completion of feeding the melt in the forming space; and after the closing step, while vibration is being applied upon the melt inside the forming space, a forming pressure is exerted upon the melt by rising the piston valve.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a process and an apparatus for producing a cast metallic product by forming a metal from a melt inside a forming space of a die under application of pressure to the melt according to a direct melt-forming method.

[0003] 2. Related Art Statement

[0004] In each of conventional metal-forming apparatuses, a cast metallic product has generally been produced by pressurizing a melt fed in a forming space in a lower die unit with an upper die unit, and compressing and solidifying it. That is, the upper die unit had a function to apply a forming pressure upon the melt. Further, since the upper die unit needed to slide in the forming space of the lower die unit, a clearance was provided between the lower and upper die units.

[0005] On the other hand, with decrease in weight of automobile parts, electric parts, etc., formed products of such as aluminum and magnesium have been frequently used. With such a tendency, improvement on strength of the formed products has been strongly demanded.

[0006] In order to increase the strengths of the formed products, it is necessary to enhance their density by preventing occurrence of inner defects such as voids. However, according to the conventional forming apparatus having the above construction, since large pressure is rapidly applied to the melt over a wide range by the upper die unit, burring occurs through clearance, so that the melt runs short in the forming space. Consequently, the melt is not sufficiently pressurized, which unfavorably causes inner defects such as voids, and decreases the density, resulting in a high percentage of formed products having unacceptable strengths. Further, the burrs formed on the formed metallic products thus obtained makes post-working more dangerous. In addition, since removal of burrs requires cutting and punch pressing, costs such as a press forming cost, a press machine-producing and installation cost and a running/maintenance cost are necessary to prevent cost-down. Further, since the forming pressure is applied by the upper die unit, the forming apparatus itself becomes bulky.

SUMMARY OF THE INVENTION

[0007] The present invention is to provide a process and an apparatus for forming a metal, which enables the production of metallic formed products having high quality and high strength.

[0008] A first aspect of the present invention is directed to the process for producing a cast metallic product by forming a metal from a melt inside a forming space of a die under application of pressure to the melt according to a direct melt-forming method, comprising the steps of:

[0009] while feeding a melt into a forming space of a lower die unit, gradually descending a piston valve closely slidable in a cylinder space to a given location in the forming space, said cylinder space being located under the casing and opened to a bottom surface of the forming space at an area smaller than that of said bottom surface;

[0010] closing the forming space with an upper die unit after completion of feeding the melt in the forming space; and

[0011] after said closing step, while applying vibration upon the melt inside the forming space, applying a forming pressure upon the melt by rising the piston valve.

[0012] The following are preferred embodiments of the present invention, and any combinations thereof are considered to be preferred.

[0013] (1) Vibration is applied to the melt during the melt-feeding step.

[0014] (2) The piston valve is raised in releasing the cast metallic product from the forming space.

[0015] The second aspect of the present invention is directed to the metal-forming apparatus for producing a cast metallic product upon application of pressure to a melt in a forming space according to a direct melt-forming method, comprising a lower die unit having a forming space, an upper die unit for closing the forming space of the lower space, a piston valve mechanism, a vibrator, and a piston valve-driving mechanism, said piston valve mechanism comprising a cylinder space and a piston valve closely slidable in the cylindrical space, said cylinder space being located under the forming space and opened to a bottom surface of the forming space at an area smaller than that of said bottom surface, wherein the piston valve-driving mechanism is controlled such that when the melt is to be fed into the forming space, the piston valve is gradually descended to a given location within the cylinder space, and when the melt-feeding step is terminated and the forming space is closed with the upper die unit, the piston valve is ascended to apply forming pressure upon the melt, and wherein when the forming pressure is applied to the melt in the forming space, the vibrator makes vibration upon the melt through the lower die unit.

[0016] The following are preferred embodiments of the metal-forming apparatus according to the present invention, and any combination thereof is considered to be a preferred embodiment of the invention apparatus.

[0017] (1) Vibration is applied to the melt through the upper die unit when the forming pressure is applied to the melt within the forming space.

[0018] (0011)

[0019] (2) The vibrator includes two vibrator units provided for the upper and lower die units, respectively.

[0020] (3) The piston valve-driving mechanism is a damper.

[0021] (4) The piston valve-driving mechanism is driven such that when the cast metallic product is to be released from the forming space, the piston valve is ascended.

[0022] These and other objects, features and effects of the present invention will be appreciated upon reading of the following description of the invention when taken in conjunction with the following description of the invention, with the understanding that some modifications, variations and changes of the invention could be easily made by the skilled person in the art to which the invention pertains.

BRIEF DESCRIPTION OF THE INVENTION

[0023] For a better understanding of the invention, reference is made to the attached drawings, wherein:

[0024]FIG. 1 is a partially vertically sectional view of a metal-forming apparatus according to the present invention.

[0025]FIG. 2 is a partially vertically sectional view of an operational state of the invention apparatus.

[0026]FIG. 3 is a partially vertically sectional view of an operational state of the invention apparatus, following that in FIG. 2.

[0027]FIG. 4 is a partially vertically sectional view of an operational state of the invention apparatus, following that in FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

[0028] The present invention will be explained in more detail with reference to the attached drawings.

[0029]FIG. 1 is a partially vertically sectional view of a metal-forming apparatus to carry out the method for producing a cast metallic product according to the present invention. The metal-forming apparatus is to produce the cast metallic product through application of pressure upon the melt inside a forming space. The apparatus includes a lower die unit 1 with such a forming space 11, and an upper die unit 3 for closing the forming space 11. The lower die unit 1 is provided with a piston valve mechanism 5 and two vibrators 7, 7 as shown, and the upper die unit 3 is provided with a vibrator 8. Between the lower die unit 1 and the upper die unit 3 is provided a clearance to allow the upper die unit to be slidable within the forming space 11.

[0030] The piston valve mechanism 5 includes a cylinder space 51 located under the forming space 11 and opened to the bottom surface 111 of the forming space 11 of the lower forming unit 1, and a piston valve 52 slidable within the cylinder space 51, and the piston valve mechanism 5 is driven by a driving mechanism 6. The open area of the cylinder space 51 to the bottom surface 111 of the forming space 11 is set smaller than the area of the bottom surface 111 of the forming space 11 and that 31 of a projected tip of the upper die unit 3. For example, the ratio of the open area of the cylinder space 51, that is, the pressing area of a valve 521 to the area of the bottom 111 is set about 1:4. The piston valve 52 includes the valve 521 slidable within the cylinder space 51 and a piston 522 having the valve 521 fixed to its tip. When the driving mechanism 6 is in no operation time, the valve 521 closes an opening 511 of the cylinder space 51 to the forming space 11.

[0031] The driving mechanism includes a damper, which is controlled by a hydraulic pump 62, a relief valve 63, a check valve 64, etc. The driving mechanism 6 is to be operated as follows. The damper, the hydraulic pump 62, the relief valve 63, and the check valve 64 constitute a driving mechanism for controlling ascending and descending the piston valve. That is, (1) the driving mechanism 6 gradually descends the valve 521 to a given location in the cylinder space 521 when the melt is fed into the forming space 11, (2) presses the valve 521 upwardly to apply forming pressure upon the melt after the melt-feeding step is terminated and the forming space 11 is closed with the upper die unit 3, and (3) ascends the valve 521 when the cast metallic product is released from the forming space 11.

[0032] Vibrators 7 are provided at opposite sides of the lower die unit 1 to apply vibration upon the melt inside the forming space 11 from the both sides thereof. A vibrator 8 is provided at an upper portion of the upper die unit 3 to apply vibration upon the melt inside the forming space 11 from the upper side thereof in the state that the upper die unit 3 closes the forming space 11. For example, vibrating motors or ultrasonic wave generators may be used as the vibrators 7, 8. However, the vibrators 7, 8 are not limited to them, so long as vibration is generated. The frequency of the vibration applied is preferably not less than 30 Hz. The vibrators 7 are set to operate as follows. That is, the vibrators 7 are turned on (1) when the melt is being fed into the forming space 11 and (2) when the forming pressure is being applied to the melt inside the forming space. The vibrator 8 is to be operated as follows. That is, the vibrator 8 is turned on when the forming pressure is being applied to the melt inside the forming space.

[0033] Next, the operation of the above-constructed metal-forming apparatus will be explained.

[0034] As the melt 2 begins to be fed into the forming space 11 in the state that the upper die unit 3 is located above the lower die unit 1, the driving mechanism 6 drives the piston valve mechanism 5 so that the piston valve 52 may be gradually descended to a given location in the cylinder space 51. Thereby, the melt 2 is poured into the forming space 11, while the melt 2 fed into the forming space 11 is being sucked into the cylinder space 51. Therefore, the melt 2 is filled in the forming space 11 with no gap. In addition, while the piston valve mechanism 5 is being driven, the vibrators 7 are turned on to apply the vibration upon the melt 2 being fed into the forming space 11. FIG. 2 shows a state in which the charging of the melt 2 is terminated.

[0035] Next, as shown in FIG. 3, the upper die unit 3 is descended to close the forming space 11. Then, while the piston valve 52 is upwardly urged inside the cylinder space 51 to apply the forming pressure upon the melt 2, the vibrators 7, 8 are turned on to apply the vibration upon the melt 2 in the forming space 11. Thus, the semi-solidified melt 2 is compressed and solidified while receiving the vibration, thereby giving a cast metallic product.

[0036] The apparatus exhibits the following functions. (1) Since the vibrators 7, 8 apply the vibrating energy to the melt 2 during forming, the motion of the metal atoms of the melt 2 are activated to uniformly array crystalline particles and prevent segregation during solidifying. In addition, since vibrating energy is also applied to the melt 2 during feeding, the above effect is more excellently exhibited. Therefore, the high-quality and high-strength cast metallic product having a uniform tissue and a high density without internal defects such as voids can be obtained. (2) Since the pressing area of the valve 521 is small, the pressure applied upon the melt 2 from the valve 521 gently spreads all over the melt 2, starting from the valve 521. Therefore, the melt 2 is prevented from entering a clearance between the lower die unit 1 and the upper die unit 3, thereby preventing the formation of burrs. Consequently, the melt does not become insufficient in the forming space 11, and the pressurizing upon the melt 2 is not insufficient. Thus, occurrence of the internal defects such as cast voids is prevented and the cast product is more densified, so that the high-quality and high strength cast metallic product is obtained. The forming pressure applied upon the melt 2 from the valve 521 is specifically preferably not less than 800 kg/cm². As the pressure applied increases, the density and the quality of the cast metallic product obtained become higher.

[0037] After the piston valve mechanism 5 and the vibrators 7, 8 are stopped, the upper die unit 3 is upwardly moved as shown in FIG. 4. Then, the piston valve mechanism 5 is driven to ascend the piston valve 52 inside the cylinder space 51 and push up the cast metallic product 20 with the valve 521. Thereby, the piston valve 52 functions as a knockout pin, so that the cast metallic product 20 is easily released from the die.

[0038] As mentioned above, the above-constructed metal-forming apparatus can perform the metal-forming process comprising (1) the melt-feeding step in which while the melt 2 is being fed into the forming space 11 of the lower die unit 1, vibration is applied to the melt 2; the piston valve 52 slidable inside the cylinder space 51 opened to the bottom surface 111 of the forming space 11 is gradually descended to a given location of the cylinder space 51, (2) the closing step in which the forming space 11 is closed with the upper die unit 3 after the feeding step, and (3) the forming step in which after the closing step, while the vibration is being applied to the melt 2, the piston valve 52 is urged upwardly to apply the forming pressure upon the melt 2.

[0039] According to the metal-forming apparatus constructed above since the vibration is applied to the melt 2 during feeding and forming, the motion of the metal atoms in the melt 2 are activated, and the segregation during the solidification is prevented. Therefore, the high-quality and high-strength cast metallic product having a uniform tissue and a high density without internal defects such as cast voids is obtained.

[0040] Furthermore, since the forming pressure is applied to the melt 2 from the piston valve 52 of the piston valve mechanism 5 provided below the lower die unit 1, the pressure is applied gently upon the melt 2 to prevent the occurrence of burrs. Thus, the melt does not become insufficient in the forming space, so that the highly densified cast metallic product is obtained, while production of an unacceptable product with occurrence of the internal defects is prevented.

[0041] Since the piston valve 52 is gradually descended to a given location of the cylinder space 51 during feeding the melt 2, the melt 2 is poured into the forming space 11, while being sucked into the cylinder space 51. Thereby, the melt 2 is filled into the forming space 11 without a gap.

[0042] So long as the vibration is sufficiently applied to the melt 2, the vibration of the melt with the vibrators 7 and the provision of the vibrator 8 are not necessarily necessary. Further, the number of the vibrators 7 is not limited to two, so long as sufficient vibration is applied to the melt 2.

[0043] Instead of the oil hydraulic pressure, pneumatic pressure or the hydraulic pressure may be used for the driving mechanism 6. 

What is claimed is:
 1. A process for producing a cast metallic product by forming a metal from a melt inside a forming space of a die under application of pressure to the melt according to a direct melt-forming method, comprising the steps of: while feeding a melt into a forming space of a lower die unit, gradually descending a piston valve closely slidable in a cylinder space to a given location in the forming space, said cylinder space being located under the casing space and opened to a bottom surface of the forming space at an area smaller than that of said bottom surface; closing the forming space with an upper die unit after completion of feeding the melt in the forming space; and after said closing step, while applying vibration upon the melt inside the forming space, applying a forming pressure upon the melt by rising the piston valve.
 2. The producing process set forth in claim 1 , wherein vibration is applied to the melt during the melt-feeding step.
 3. The producing process set forth in claim 1 or 2 , which further comprises a step of raising the piston valve on releasing the cast metallic product from the forming space.
 4. A metal-forming apparatus for producing a cast metallic product upon application of pressure to a melt in a forming space according to a direct melt-forming method, comprising a lower die unit having a forming space, an upper die unit for closing the forming space of the lower space, a piston valve mechanism, a vibrator, and a piston valve-driving mechanism, said piston valve mechanism comprising a cylinder space and a piston valve closely slidable in the cylindrical space, said cylinder space being located under the forming space and opened to a bottom surface of the forming space at an area smaller than that of said bottom surface, wherein the piston valve-driving mechanism is controlled such that when the melt is to be fed into the forming space, the piston valve is gradually descended to a given location within the cylinder space, and when the melt-feeding step is terminated and the forming space is closed with the upper die unit, the piston valve is ascended to apply forming pressure upon the melt, and wherein when the forming pressure is applied to the melt in the forming space, the vibrator makes vibration upon the melt through the lower die unit.
 5. The metal-forming apparatus set forth in claim 4 , wherein vibration is applied to the melt through the upper die unit when the forming pressure is applied to the melt within the forming space.
 6. The metal-forming apparatus set forth in claim 4 or 5 , wherein the vibrator includes two vibrator units provided for the upper and lower die units.
 7. The metal-forming apparatus set forth in any one of claims 4 to 6 , wherein the piston valve-driving mechanism is a damper.
 8. The metal-forming apparatus set forth in any one of claims 4 to 6 , wherein the piston valve-driving mechanism is driven such that when the metallic cast product is to be released from the forming space, the piston valve is ascended. 